Magnetic hammer and method of making same



Jam. 28, 1958 w, MOUNT 2,821,222

MAGNETIC HAMMER AND METHOD OF MAKING SAME Filed April 13, 1953 INVENTOR Ereurge W. Mnun'i:

I BY

ATTORNEYS United States Patent MAGNETIC HAMMER AND METHOD or MAKING SAME This invention relates to an improvement in magnetic hammers.

It is the principal object of the invention to provide a construction, suitable for upholstering and other uses in which the magnetic field is concentrated at the striking face of the hammer.

A further object is to provide a construction in which the most eflicient type of permanent magnet may be used in a manner to take full advantage of its strength and permanent qualities.

Other and further objects and advantages will be made apparent in the disclosure of the accompanying drawing and the following specification and claims.

This application is a continuation in part of my prior application Serial No. 265,034 filed January 4, 1952, now Patent No. 2,731,993.

In the accompanying drawing,

Fig. 1 is a side elevational view of a hammer embodying the invention;

Fig. 2 is a fragmentary view, partly in section and on a larger scale, showing the details of construction; and

Fig. 3 is a diagrammatic view illustrating a preferred step in the manufacture of the hammer.

Referring to the drawings the body of hammer head is indicated at 1. The form of hammer shown is of the type having two strikin surfaces, as indicated at 2 and 3, and commonly employed by upholsterers.

The body 1 is formed of a non-magnetic material such as brass, bronze or similar alloy. Preferably the body of the head is cast from a silicon-bronze alloy. Since these non-magnetic alloys are relatively soft the striking faces are provided with steel discs or caps 4 soldered, welded or brazed in place. The discs 4 are of sufficient hardness to withstand driving impact in use.

As best shown in Fig. 2 one end of the head is bored as indicated at 5 to form a chamber opening to the adjacent end face of the head. A cylindrical magnet 6 is fitted in the chamber 5. This magnet is of the so-called permanent type, formed of one of the powerful permanent magnet Alnico alloys, the essential ingredients of which are iron, nickel and aluminum, also sometimes c0- balt and copper.

After the bore 5 has been formed the permanent magnet 6 may be inserted in the bore and the steel disc 4 welded, silver soldered or brazed in place. Preferably and for efficiency in operation the length of magnet 6 should be approximately five times its diameter. As shown the depth of bore 5 and the length of magnet 6 should be closely equal so that when the disc 4 is fixed in place the magnet is held against movement.

The heat necessary in welding, soldering or brazing the disc 4 in place tends adversely to efiect the magnet in the bore and to reduce its strength. If care is exercised and the minimum of heat essential to adequately bonding the steel disc to the nonmagnetic material of the head is employed, a satisfactory hammer for the purpose is produced. Preferably and advantageously, however, the magnet member 6 is positioned in bore 5 in an M 2,821,222 1C6 Patented Jan. 28, 1

unmagnetized condition and'theend of the head and the member 6 are smoothed, as by grinding in a single operation to render the end surfaces of the hammer body and magnet flush with eachother, after which the disc 4 is secured in place. Thereafter the hammer, as diagrammatically shown in Fig. 3, is placed between the pole pieces 7 and 8 of the core 9 of an electromagnet, the coil of which is indicated at 10. The pole piece -7 is forked as indicated at 11 to straddle the hammer head with the inner sides of the forks engaging the adjacent sides of the head while the pole piece 8 engages the center of disc 4. The distance between the pole pieces is such as to position the forks of the pole piece adjacent the rear end of magnet member '6 positioned within the bore 5. When current is applied to coil 10 in the usual manner from a suitable source, not shown, the member 6 is permanently magnetized in situ, thus avoiding subsequent alteration of the magnetic characteristics of the magnet from the heat of a soldering or welding operation. This method tends further to concentrate the magnetic strength at the striking end.

The position of the magnet at substantially right angles to the striking face of the head and the fact that the steel striking element 4 is in contactwith the end of the magnet concentrates the magnetic strength at the striking face. The taper of the non-magnetic body of the head toward the striking face further tends to increasingly reduce the effectiveness of the magnetic field around the head rearwardly of the disc, the lines of force meeting increasing resistance towards the rear end of the magnet. Since the disc 4 is of the full diameter of the end of the body portion the force of the driving blow when the hammer is used is distributed throughout the body of the head.

By forming the entire body of the hammer head of nonmagnetic material, providing a striking element in the form of a steel disc or cap at the striking end of the hammer, and embedding the magnet axially in the nonmagnetic body, with the end of the magnet in contact with the disc, the diameter of the magnet being not substantially more than half the diameter of the hammer body and of the cap where the body and cap are joined together, in effect provides a non-magnetic hammer head with a magnetic striking face. In other words, the magnet magnetizes only the steel end striking portion of the hammer represented by the relatively thin disc 4, the latter being maintained in a permanently magnetized condition by the permanent magnet and forms a pole piece or load lifting armature for the magnet by which the tacks or nails are carried in the operation of the hammer. Since in the magnetic system described the magnetism of the member 4 is derived from and maintained by the permanent magnet 6, the degree of hardness of members 4 need be no greater than that needed to perform its function as the striking element of the hammer, and the selection of the type of steel for the discs 4 may therefore be made on the basis of the physical service the hammer is to perform and the manufacturing costs involved without substantially effecting the magnetic properties of the hammer as a whole.

What is claimed is:

1. The method of making a magnetic hammer head which comprises forming the head from a non-magnetic alloy, forming a bore opening to the striking end of the head and extending therefrom axially of the head, inserting a piece of permanently magnetizable metal in said bore, said piece having a length and diameter substan t-ially equal to the length and diameter of the bore, grinding the said end of the head and the adjacent end of said piece in a single operation to render the end surfaces of the head and said piece flush with each other, permanently brazing a steel disc to said end of the head in contact with said piece to close said bore and form the striking element of the head, and thereafter permanently magnetizing said piece in situ to maintain the disc in a permanently magnetized condition.

2. In a magnetic type hammer comprising a head formed of a non-magnetic metal alloy and provided with an axially extending cylindrical bore, the inner end of the here being closed and its outer end opening substantially centrally of the face of the striking end of the head, a cylindrical bar formed of magnetizable Alnico alloy fitted in said bore with its inner end engaging the non-magnetic alloy of the head at the inner end of the bore and its outer end surface flush with the adjacent surface of the striking end of the head, said surfaces being finished to present a smooth surface in a common plane, and a steel disc coextensive with the striking end of the hammer and of sufficient hardness for driving purposes permanently brazed to the finished surface only of the striking end of the head, the diameter of the bore and bar being not substantially greater than one-half the diameter of the head and disc where the head and disc are brazed together, the finished surface of the bar contacting said disc in said plane, to form with said disc 21 jointly magnetizable system in the head adapted for subsequent magnetization.

3. A magnetic type hammer having a head formed of a non-magnetic metal alloy and provided with an axially extending cylindrical bore, the inner end of the bore be- 4 ing closed and its outer end opening substantially centrally of the face of the striking end of the head, a cylindrical bar formed of magnetizable Alnico alloy fitted in said bore with its inner end engaging the non-magnetic alloy of the head at theinner end of the bore and its outer end surface flush with the adjacent surface of the striking end of the head, said surfaces being finished to present a smooth surface in a common plane, and a steel disc coextensive with'the striking end of the hammer and of sutficient hardness for driving purposes permanently brazed to the finished surface only of the striking end of the head, the finished surface of the bar contacting said disc in said plane, said bar and disc being unitarily permanently magnetized in place to jointly form the magnetic system of the hammer, the diameter of the 'bore and bar being not substantially greater than one half the diameter of the head and disc where the head and disc are brazed together.

References Citedin the, fileof this patent UNITED STATES PATENTS p 29,760 Boelken Aug. 28,1860 2,550,775 Clark May 1, 1951 2,671,483 Clark May 9, 1954 FOREIGN PATENTS 801,446 Germany NOV. 30, 1950 

